CA->Fed VX conversion won't pass smog :(

[GasSavers_mango]

Ayudame with your knowledge, amigos! I posted this question on ecomodder but didn't get too many valuable responses. I'm hoping some wise GS sages can shed some light.


I converted my 94 vx from CA to Fed in 7/08. To my surprise, the conversion went off without a hitch. I went from low to mid 40s to averaging 51mpg in my mostly city commute. (me=very happy). When I did the conversion, I made sure to shield the wiring. I also left the original 4 wire plug intact so I could switch back if need be.

In 10/09, it came time to get smogged again. I wasn't able to pass in Federal mode. It came down to crunch time, and I swapped the ECU and o2 sensor back to CA versions, and passed no problem. I love the mpgs of Fed mode, but don't want to be a gross polluter! Could you guys help me figure out what's going on?

Original test in Fed mode:


Tune up- cap, rotor, wires, plugs ZFR4F-11, air filter


Replaced Bosch L1H1 wideband o2 sensor with NTK L1H1 wideband o2 sensor. Ran tank very low then added a little 100 octane gas at Smog shop's recommendation.


Finally I ran out of time and put the old CA L01 ECU and 4 wire CA o2 back in and passed no problem


Subsequently, I checked my soldering/wiring, redid my ground with a nice gold ring term (not sure what it's called exactly), and tried an A00 ECU instead of A01. Just by giving it the sniff test, I can't say I've noticed any improvement in Fed mode emissions.

My only small suspicion is that there is about an inch of exposed wiring without shielding at both ends of where I did the new wiring. Could that be enough to mess me up? Lean burn mode is still working very well; I notice with pedal feedback and acceleration and also by my mpguino.

The car has 220K miles on it, but runs really really well. There is not suspicious behavior with the car that would make me suspect any problems had I not failed smog.

Has anyone that's done the conversion from CA->Fed on a '93 or older VX successfully passed smog?

Also, does anyone have any recommendations how I can accurately check my emissions for cheap now that I don't need to get my car smogged? The sniff test I'm sure is very bad for me and also inaccurate. It was nice finding a smog place that wouldn't charge me until I passed, but I ran out of time.

Thanks in advance!

[101mpg]

As a former Californian I am very familiar with the smog tests. The problem with smog testing in California is that they only check parts per million, not how many millions of parts you're actually putting out of any given pollutant or non-pollutant.

If you're 5% over on a particular pollutant - Nitrous Oxide at 15 MPH and that is why you are failing - first off - are you putting out 90% of your driving at 15 MPH or 70 MPH? If you're getting 40 MPG with CA equipment and 51 MPG with Fed equipment - the math bears it out - you're putting out less ACTUAL pollutants because you're using LESS gasoline 28% less. I wouldn't worry about it. 5% of 28% is 1.4%, giving you a total of 26.5% LESS POLLUTANTS PUT INTO THE AIR.

Think about how much gasoline a Hummer consumes getting four people to a destination vs. how much a VX consumes.

Now - all that said - you can also pass by putting some "guaranteed to pass" (it's a fuel additive - may have to go to a nearby state to get some) in your tank. Just because you have a particular test fail doesn't mean you're a gross polluter, either. Just means the finicky smog testing may have pointed out a symptom of something, not that it pollutes much in normal traffic. Hopefully you did your smog test with the car hot, on a cool day. Cold car on a hot day will also make your smog testing results go in the wrong direction.

I have a hunch your O2 sensor and/or catalytic converter may have been the issue. You replaced the O2 sensor and the computer in tandem and it passed. With 220K miles and a lot of formulation changes in the gasoline that car has sampled over its lifetime (burning over 5500 gallons of fuel in that time), the catalytic converter may be fouled. That would be my guess.

We've seen a few of these on here. The Fed version runs a lot better than the CA version, and the CA version works just barely due to the worsening smog requirements.

In CA you're supposed to get at least one retest for free but the good ones will let you retest until you pass. I'd leave the Fed computer in there, swap out for the test, and dump a bottle of "guaranteed to pass" in the tank before you test next time. Know you're burning a LOT less fuel - as much as HALF or more than guzzlers next to you on the freeway.

[imzjustplayin]

I've heard of some people using federal ECUs and getting their cars to pass smog in California just fine. The only thing I can think of is to adjust the valve lash of the valves and just make sure the car is in tip top shape. If you don't want to have to use a California ECU every time you smog, my suggestion is to do a complete overhaul.

Just remember that you've got 220K miles on it, its emission's profile isn't going to be like that of a new car. There is a reason why Honda has a Fed and California ECU, it's partially because the car would likely fail smog earlier in life in California with the FED ECU so in order to prolong its useful life, they de-tune the ECU.

It wouldn't be too unreasonable to give the engine a good overhaul and make it like new again.. Also you might want to clean out the EGR, throttle body, etc. To put things into perspective in terms of your emissions, my '98 Civic LX had 0 HC and 0 CO 300 NOX when I did smog and it's got 175K miles on the clock! Yes I'm aware it's not a lean burn engine but these vehicles are definitely capable of a cleaner emissions profile and your vehicle failing with the Federal ECU but passed with the California ECU just shows that your vehicle is on a downward trend...if it doesn't fail today, it'll fail in a few years from now. Assuming your plugs and spark are perfect (and are using ONLY OEM recommended spark plugs!!!), the things left that would hurt emissions are partially clogged injectors, carbonized combustion chamber and worn piston rings. If you can afford to live without the vehicle for some time, I'd rebuild it because it's better to rebuild the vehicle while everything is ok than when the engine is fubared. If you rebuild the engine before things start to really wear down, you won't have to bore down the cylinder walls or anything of the sort.